Estimate Cotton Water Consumption from Shallow Groundwater under Different Irrigation Schedules
Round 1
Reviewer 1 Report
The Paper No 1535155 “Estimate cotton water consumption from shallow groundwater under different irrigation schedules” aimed to determine how the groundwater level affects the cotton water supply. The work is not well structured, the order of presentation is not clear; it can be confusing to readers. Authors did not clearly elaborated novelty of their research. In Materials and methods important information is omitted for further understanding of the work. Many symbols are not explained. The experiment should be described in more details, especially 14 hypothetical treatments (how I understand). If I am wrong, that it should be better explained.
The model calibration is not well documented and described. Whether the actual measured groundwater depths were used and what was the agreement of the model with the variations of the groundwater depth during the cotton growing season and meteorological characteristics. Crop cover (CC) and LAI are mentioned without the data displayed or the reference from where the values were taken. For example, Figure 1 shows the volumetric water content at 20 cm and the groundwater level. It is logical to expect in the section Results simulated values of both SWC and groundwater, at least for model calibration. In other words, the variation in groundwater levels should be added to Figs. 2 - 4.
The authors cite 14 models and different groundwater depths, without stating whether or not groundwater depths have gradually decreased due to capillary rise and water consumption, or when this trend has ceased to have an impact (for example starting water depth was 1m and dropped till 1.5 m after 30 days. The authors should explain in detail the 14 treatments, what was assumed (initial groundwater level) and what was actually taken from the measurements (irrigation depth, starting soil water content, climatic parameters, ETo, sowing date, etc.).
For example, from Table 7 it can be stated that the water level did not fall on treatment A1 and A2, because irrigation was not necessary, then it is necessary to state it in the text. If the groundwater level in the A7 treatment is 4 m, it is not clear how the young plant (at emergency stage) received water, unless the soil was completely wetted and the potential evapotranspiration was not great during that period. The authors do not state the climatic conditions anywhere, but commented on them in the paper. The discussion should be more extensive. The text is in italics from lines 320 - 354, so it is not clear whether it is a quote (citation) from a paper or a typo. If the quote is then a reference is missing.
Comments for author File: 
Comments.pdf
Author Response
The Paper No 1535155 “Estimate cotton water consumption from shallow groundwater under different irrigation schedules” aimed to determine how the groundwater level affects the cotton water supply. The work is not well structured, the order of presentation is not clear; it can be confusing to readers. Authors did not clearly elaborated novelty of their research.
Answer: I agree this point. I have emphasized the novelty in revised manuscript. The novelty was showed two aspects: the first, a new function (equation 6) was established in correlation with the surface soil water content, crop cover and reference crop evapotranspiration to calculate the soil evaporation and determine the evaporation partition. These factors were calculated using the days after sowing and did not require observations. which was not reported by previous studies. It will provide a better way to interpret evapotranspiration partitioning and to model water consumption in cotton field. Line 84-89.
The second, although the HYDRUS model can simulate irrigation and water consumption at a given groundwater table, the model can only set a fixed or initial groundwater table. In practice, changes in groundwater table are not entirely depend on evaporation consumption from cropland (but lysimeter with impermeable bottom), but involve lateral recharge and groundwater consumption from surrounding areas. Our model takes into account an actual groundwater change (groundwater variation with time as an input parameter), which better reflects a real situation. Line 96-103, line 238-241.
In Materials and methods important information is omitted for further understanding of the work. Many symbols are not explained. The experiment should be described in more details, especially 14 hypothetical treatments (how I understand). If I am wrong, that it should be better explained.
Answer: I agree this point, some important information was omitted, thus cause some misunderstanding for reader. I added statement to explain our experiment and model. Line 155-162, line 170-171, line 184, line 206-207.
We added statements for 14 hypothetical treatments: the groundwater table fluctuation had a range from 1.4 m to 3.1 m during growing season in 2010 and 2011 (Fig 1), the modeling scenarios cover this range to reflect the real situation, thus we conduct seven groundwater tables from 1.0 to 4.0 m. line 231-234.
For each scenario, the groundwater table time series were generated by adding a constant value (ranging from −1.5 to 1.5 m) to the groundwater table depth measured in 2010, it was as an input parameter to run the model (Fig 2). The mean groundwater table was 2.5m (measured value during growing season) in 2010, the seven groundwater table (mean value) were conducted as follow: 1.0 m [2.5m+ (-1.5m)], 1.5 m [2.5m+(-1.0m)], 2.0 m [2.5m+(-0.5m)], 2.5 m (2.5m+0m), 3.0 m (2.5m+0.5m) , 3.5 m (2.5m+1.0m) and 4.0 m (2.5m+1.5m) (Table 5), respectively, all the change trend of groundwater tale (14 treatments) was consistent with measured data in 2010 during growing season (fig 2). Line 238-249.
The model calibration is not well documented and described. Whether the actual measured groundwater depths were used and what was the agreement of the model with the variations of the groundwater depth during the cotton growing season and meteorological characteristics.
Answer: My apologize, it’s cause misunderstanding due to omitted some important statement. The groundwater depths were input parameters, only soil moisture was used to calibrated model. Line 238-249.
Crop cover (CC) and LAI are mentioned without the data displayed or the reference from where the values were taken. For example, Figure 1 shows the volumetric water content at 20 cm and the groundwater level. It is logical to expect in the section Results simulated values of both SWC and groundwater, at least for model calibration. In other words, the variation in groundwater levels should be added to Figs. 2 - 4.
Answer: the LAI was added in “Materials and methods”, line 170-171. The “CC” has not been measured. Actually, the equations (6) doesn’t include a measured parameter “CC”, the CC were reflect by the last term (power function). Line 206.
The authors cite 14 models and different groundwater depths, without stating whether or not groundwater depths have gradually decreased due to capillary rise and water consumption, or when this trend has ceased to have an impact (for example starting water depth was 1m and dropped till 1.5 m after 30 days.
Answer: my apologize again, it’s cause misunderstanding due to omitted some important statement. The groundwater depths were input parameters to run model, the variation of groundwater depths was showed in fig 2 (new figure). We assumed that the groundwater table was natural fluctuation, which was not influenced by water consumption from cropland. Line 238-249, line 97-101.
The authors should explain in detail the 14 treatments, what was assumed (initial groundwater level) and what was actually taken from the measurements (irrigation depth, starting soil water content, climatic parameters, ETo, sowing date, etc.).
Answer: we added information in “Materials and methods”, line 238-249.
For example, from Table 7 it can be stated that the water level did not fall on treatment A1 and A2, because irrigation was not necessary, then it is necessary to state it in the text. If the groundwater level in the A7 treatment is 4 m, it is not clear how the young plant (at emergency stage) received water, unless the soil was completely wetted and the potential evapotranspiration was not great during that period.
Answer: we added information in “Results and Discussion”, line 313-321.
The authors do not state the climatic conditions anywhere, but commented on them in the paper. The discussion should be more extensive.
Answer: we added information in “Results and Discussion”, line 359-369. The variation of ET0 with time was added in figs 7 c .
The text is in italics from lines 320 - 354, so it is not clear whether it is a quote (citation) from a paper or a typo. If the quote is then a reference is missing.
Answer: It’s mistake, the font should be consistent with other text, revised.
Reviewer 2 Report
Line 139: Please refer the required info for the neutron probe that you used
Lines 209-201: Please consider moving the presentation of the scheduling methods that you followed, to 2.2.2 Field experimental design
Lines 231-237: Please make equal the size of the indivindual diagrams of Figs 2 and 3
Author Response
Line 139: Please refer the required info for the neutron probe that you used
Answer: we added information for neutron probe, line 155-162.
Lines 209-201: Please consider moving the presentation of the scheduling methods that you followed, to 2.2.2 Field experimental design
Answer: my apologize, it’s cause misunderstanding due to omitted some important information. This section was scenario simulation, rather than the real experiment observation. I added some statement to explain it, line 238-249. thus it's not appropriate to move to 2.2.2 Field experimental design, do you agree ?
Lines 231-237: Please make equal the size of the indivindual diagrams of Figs 2 and 3
Answer: we have modified the size of fig, make equal the size as can as possible.
Round 2
Reviewer 1 Report
The paper has been improved, but some typos still have to be corrected. Please pay attention to lines 44, 130, 170, 206 and 248 (easy to see in pdf file).
Author Response
The paper has been improved, but some typos still have to be corrected. Please pay attention to lines 44, 130, 170, 206 and 248 (easy to see in pdf file).
Answer: thanks for your suggestion, revised, line lines 44, 130, 170, 206 and 248.
